1. Field of the Invention
The present invention relates to containers for use in packaging, storing and mixing dental amalgams for use by dentists in filling teeth.
2. Description of the Prior Art
Dental alloys are comprised of a mixture of metals which are soft and pliable immediately upon mixing, but which thereafter rapidly harden to form a rigid material for filling cavities drilled in teeth.
In the past, dental alloy capsules have included mercury and silver, which have been stored in a common container until use. However, separation between the alloy metals prior to purposeful mixing has been achieved only with great difficulty. In a conventional dental alloy container, or capsule, the confining structure is typically formed by a receptacle, a separating insert, and an enclosing cover. Typical dental alloys include a small quantity of liquid metallic mercury, and a quantity of a precious metal, such as silver or gold. The precious metal is normally packaged as a quantity of the metal, finely ground to form a powder, and compressed into a pellet. When the mercury and precious metal are mixed together, the mixture forms a dental amalgam or alloy which can be pressed into the vacancy left in a tooth by removal of decayed material. Upon mixing the mercury and precious metal, a dental alloy is formed which is soft and pliable and readily conforms to the configuration of the vacancy, or cavity in a tooth to be filled. Very shortly, however, the alloy permanently hardens, and thereafter forms a hard, durable alloy, highly resistent to chemical reaction or degradation.
Because the amalgam hardens so quickly, it is extremely important for the mercury and precious metal to be maintained in isolation from each other prior to use. With prior dental alloy containers, this has been achieved by first placing a drop of mercury in a concave receptacle, and thereafter placing an insert in the receptacle to define a cavity containing the mercury. The insert is equipped with ports, however, which provide access between the mercury cavity and the overall enclosure within the capsule at the appropriate time. These ports are sealed by the edges of a threaded cover in which the powdered gold or silver pellet and a pestle ultimately used in mixing the amalgam, are first positioned. To effectuate separation of the precious metal from the mercury in packing the container, it is necessary to carefully tilt the receptacle and the cover almost to a horizontal position, and in facing relationship. The two portions are thrust together and rapidly threadably engaged before the mercury is able to leave the cavity defined between the insert and the receptacle and to contact the silver pellet.
To prevent premature contact between the silver and mercury, the silver is compressed into a pellet and a pestle is placed on top of the pellet in the cover. This allows the cover to be tilted farther toward the receptacle without premature mixing. However, it is extremely difficult to obtain a uniform weight from pellet to pellet of the silver. In the manufacture of pellets, a cavity is first filled with powdered silver, the cavity is leveled, and the silver is compressed. The weight between pellets may vary by as much as 15 to 20 miligrams, however. This leads to inconsistencies in the alloy properties after ultimate mixing.
With deft manual dexterity, the task of packaging the mercury and silver pellets separately from each other in conventional containers can be performed. However, any hesitancy in tightening the cover to the receptacle, or tilting of either the cover or receptacle to far toward the horizontal will result in contact between the mercury and the precious metal, so that the quantity of amalgam formed hardens rapidly and becomes useless.